With the recent increase in the number of people enjoying baseball, a baseball practice system, such as a so-called screen baseball system, has emerged, which overcomes the limitations of playing baseball in a large baseball stadium and allows people to enjoy playing a virtual baseball game while experiencing virtual reality, even in a small indoor space.
Typically, a screen baseball system is installed in an indoor space and has a batting area with a space of a predetermined size in which a user can bat and a screen capable of displaying a virtual baseball diamond. When a pitching machine installed on the back of the screen pitches a ball toward the batting area, a user who is ready to hit the ball in the batting area hits the ball pitched by the pitching machine. At this time, a sensing device senses the movement of the pitched ball and the movement of the ball hit by the user. Subsequently, based on the result of sensing, whether the pitched ball is a strike or a ball is determined, and an image simulating the trajectory of the hit ball is realized on the screen.
The pitching machine used in the baseball practice system, such as the screen baseball system, pitches balls at various pitching angles and various speeds such that a user can hit the balls pitched with various types of pitches and the balls pitched at various speeds, whereby the user may take a batting practice or may enjoy a baseball game through batting.
In the baseball practice system, it is required for the pitching machine to accurately pitch balls at set pitching angles and speeds. In the case in which the pitching machine is inclined due to the installation environment, however, it is not possible for the pitching machine to pitch a ball at an accurate pitching angle. In addition, the speeds of balls pitched by pitching machines may be different from each other due to manufacturing errors or defects in the parts constituting individual pitching machines. As a result, it is not possible to accurately control the speed of the ball pitched by the pitching machine, and it is very difficult for the pitching machine to pitch the ball with uniform accuracy.
For example, in the case in which baseball practice systems, each including a pitching machine configured to pitch balls using a wheel, are installed at sites, the pitching machines at the respective sites may pitch the balls at different speeds due to mechanical variation in the pitching machines even when the balls are pitched by the pitching machines in the state in which the rotational speeds of the wheels are the same.
In addition, the ball may be pitched by the pitching machine under conditions different from the pitching conditions set for pitching machine due to deterioration of the pitching machine over time or due to a change in the weight or the state of the ball.
The related art is disclosed in prior art documents, such as Korean Patent Application No. 10-2015-0041844, Korean Patent Application No. 10-2015-0041861, Korean Patent Application No. 10-2014-0054105, Registered U.S. Pat. No. 5,443,260, and Japanese Registered Patent No. 4743763.